In order to determine the increase in boiling point of a solvent due to the presence of a solute, we use the formula:
ΔT = Kb * m * i
Here, Kb is a property of the solvent, so remains constant regardless of the solute. Moreover, because the concentration m has been fixed, this will also not be considered. In order to determine which solute will have the greatest effect, we must check i, the van't Hoff factor.
Simply stated, i is the number of ions that a substance produces when dissolved. Therefore, the solute producing the most ions will be the one causing the greatest change in boiling point temperature.
